1. Field of the Invention
The present invention generally relates to a transmitting and receiving apparatus and more specifically to a portable compact transmitting and receiving apparatus having a casing accommodating an antenna and a battery.
2. Description of the Related Art
Recently, a positioning system based on an Ultra Wide Band (UWB) radio technology using wide band radio waves has been investigated. The positioning system includes a system for determining the position of a customer who is in a shop, for example. In the system, a transmitting and receiving apparatus (UWB tag) is provided to be carried by a customer or mounted on a shopping cart used by the customer in the shop. Further, plural communication devices (base stations) separated from each other are provided in predetermined areas in the shop. The position of the customer is detected by the signal communications between the transmitting and receiving apparatus and the communication devices.
In this case, the transmitting and receiving apparatus is desired to be thin and compact because it is assumed that the customers wear straps of the transmitting and receiving apparatuses around their neck in practical cases.
The applicant et al. of the present invention have applied a plane antenna including a home-plate shaped element pattern and a substantially square-shaped ground pattern disposed in the vicinity of the element pattern as a UWB antenna. The UWB antenna is preferably used for a thin transmitting and receiving apparatus. In addition, preferably, a button cell battery may be used to reduce the thickness of the transmitting and receiving apparatus.
Unfortunately, in the technical field of the UWB antenna for such a portable apparatus, no remarkable research focusing on how a layout of the element pattern and the button cell battery influences the antenna characteristics has been made.